In recent years, the ferroelectric memory field-effect transistor (FEMFET) is widely applied to the non-volatile ferroelectric random access memory (NVFeRAM) since the ferroelectric memory field-effect transistor is capable of nondestructively reading and raising the integration of components. The wide memory window and fast read/write abilities have been researched and disclosed. However, in U.S. Pat. Nos. 6,449,185 and 6,285,577, the memory retention time of the ferroelectric memory field-effect transistor is less than 105 seconds, even few seconds, and the crystallization temperature of the ferroelectric thin film has to be above 600° C. The low memory retention time and high crystallization temperature must be overcome for industrial applications.
In order to effectively extend the memory retention time, according to the theories, the followings should be carried out under low voltage operation.
(1) raising a ratio of remnant polarization (Pr) to polarization saturation (Ps);
(2) lowering the leakage current density of an insulating layer; and
(3) lowering a ratio of a ferroelectric thin film area to an insulating film area in the metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structure to obtain a better capacitance matching between MFM and MIS.
Therefore, it is an object of the present invention to provide a MgO doped BST thin film to be served as an insulating layer having thermal stability, low current leakage density and high dielectric constant, a LaNiO3(LNO) to be served as a metal oxide electrode, and a BixLa4−xTi3O12(BLT) to be served as a ferroelectric material. The advantages of the present invention are not only to extend the memory retention time more than 106 seconds (AF/AI= 1/12 and 1/16), but also to lower the fabrication temperature of BLT ferroelectric thin film due to forming a ferroelectric film on the LNO oxide.